Recently, vehicles have been provided with various diagnosis functions, such as those provided in a self diagnosis system (e.g., an On-Board Diagnosis (OBD) system). An example of such a diagnosis function may be monitoring leakage of a fuel supply system. Usually, a vehicle is equipped with a fuel level sensor for detecting the amount of fuel stored in the fuel tank.
The above-mentioned fuel leakage monitoring may function depending on the operation of the fuel level sensor. For example, in the case where the difference between the value of the fuel level detected at the fuel level sensor, and the filtered value (e.g., a low-pass filtered value) is large, the fuel leakage monitoring function may be stopped.
When the difference between a raw detected value and its filtered value of the fuel level sensor is high, it may imply that a fluctuation of fuel in the fuel tank is large. In this case, the fuel leakage monitoring is stopped in order to prevent a wrong diagnosis.
According to such a prior art, the possibility of noise in the fuel level sensor is not considered. However, it is notable that there may be a big difference between the raw detected value and the filtered value in the case where the signal received from the fuel level sensor has a lot of noise.
That is, according to the prior art, when the fuel level sensor is in a noisy failure state, such a failure is not diagnosed nor is the fuel leakage monitoring function performed.
Therefore, if a method for diagnosing noisy failure of a fuel level sensor of a vehicle is provided, the self diagnosis function of the vehicle and the fuel leakage monitoring function may be enhanced.